Concentration Polarization Phenomenon Research Articles

Pengaruh Tekanan Transmembran dan Konsentrasi Chemical Cleaning Agent (NaOH) pada Penyisihan Fosfat dari Limbah Laundry dengan Membran Ultrafiltrasi Aliran Cross Flow

The rapid economic development and community activities increasingly crowded cause appearance laundry business that effect on the environment. Ultrafiltration membrane is one of wastewater treatment technologies, but membranes have limitations such as the occurrence of the phenomenon of concentration polarization and fouling. The research objective of this study the effect of variations in transmembrane pressure against the rejection percentage Phosphate and the effect of variations in transmembrane pressure, concentration of washing of the efficiency and effectiveness of washing the membrane. the concentration of the washing of the efficiency and effectiveness of washing the membrane. The process of ultrafiltration membranes and membrane chemical washing wastewater laundry do with variations in pressure of 1 bar , 2 bar , and 3 bar. Variation of chemical cleaning agent concentration of 1%, 1.5% and 2%, rinsing with distilled water for 30 minutes, filtering wastewater laundry for 120 minutes, and washing using chemical cleaning agent (NaOH) for 30 minutes. Results highest percentage of rejection was 82.9% for Phosphate parameters in transmembrane pressure of 3 bar. The highest washing efficiency of the value of Flux Recovery (FR) gained 81.9%, and the value of resistance of Removal (RR) gained 82.59% with a concentration of 2% in the transmembrane pressure of 3 bar. The highest leaching effectiveness obtained at 50.21% with a concentration of 2% and a transmembrane pressure of 3 bar.

Thin PdCu membrane for hydrogen purification from in-situ produced methane reforming complex mixtures containing H2S

A 0.9 µm PdCu (69 wt% Pd) membrane prepared by an electroless plating method on a ceramic tubular support was tested in hydrogen sulfide containing streams. H2S/H2 mixtures with 40 and 100 ppmv of H2S were tested in order to observe the reversibility of sulfur addition. The membrane permselectivity operating in H2S/complex mixtures with around 32 ppmv of H2S in CH4, CO, CO2 and H2 was also tested. The streams were in-situ produced by Methane Steam Reforming and Methane Catalytic Partial Oxidation reactions. Prior to the tests with H2S, the hydrogen flux of the membrane at 773 K and 2 bar of pressure difference was 0.92 mol m−2 s−1. Membrane hydrogen flux decreased by around 50–80% in the tests with H2S/H2 mixture, but it recovered to the original values after removing H2S. In H2S/complex mixtures operation, the flux decrease was smaller due to concentration polarization phenomena. Although no sulfide compounds where detected on the membrane by SEM−EDX, XRD or XPS, the H2S or the employed temperatures seem to induce Cu segregation to the membrane surface.

Water-Stable Metal–Organic Framework UiO-66 for Performance Enhancement of Forward Osmosis Membranes

Forward osmosis (FO) is an emerging technology for environmental applications such as seawater desalination and wastewater treatment. However, the lack of long-term water stability and internal concentration polarization (ICP) phenomenon of FO membranes are the key challenges limiting its impact in real practice. In this study, we explore the use of water-stable metal–organic framework UiO-66 in different concentrations as fillers for the fabrication of high-performance and water-stable FO mixed-matrix membranes (MMMs) with mitigated ICP. The influences of UiO-66 on the phase inversion pathway and postinterfacial polymerization reaction cause changes in membrane morphology and chemistry, reducing the membrane structural parameter (S) and mitigating the ICP effect. As a result, the best performing FO membrane (6.5 wt % UiO-66) exhibits a 50% increased water flux over the pristine membrane, when deionized water and 1 M NaCl are used as the feed and draw solutions, respectively. The extent of ICP mitigation ...

Effect of advection on transient ion concentration-polarization phenomenon.

Here, we studied the effect of advection on the transient ion concentration-polarization phenomenon in microchannel-membrane systems. Specifically, the temporal evolution of the depletion layer in a system that supports net flow rates with varying Péclet values was examined. Experiments complemented with simplified analytical one-dimensional semi-infinite modeling and numerical simulations demonstrated either suppression or enhancement of the depletion layer propagation against or with the direction of the net flow, respectively. Of particular interest was the third-species fluorescent dye ion concentration-polarization dynamics which was further explained using two-dimensional numerical simulations that accounted for the device complex geometry.

Effects of organic, biological and colloidal fouling on the removal of pharmaceuticals and personal care products by nanofiltration and reverse osmosis membranes

The impact of different foulant composition and pHs on the removal of pharmaceutical and personal care products (PPCPs) by nanofiltration (NF270 and NF90) and reverse osmosis (XLE) membranes was investigated in this study. Humic acid (HA), alginate (SA) and silica (Si) were used for the formation of organic, biological and colloidal fouling, respectively, and were further mixed for the formation of composite fouling on membrane surfaces. The results show that significant flux decline was observed with decreasing pH and all kinds of foulant composition for the three membranes, which was contributed mostly by irreversible fouling, especially for the tight XLE. Moreover, the trends of flux decline and particle size of composite foulants at different pHs were dominant by HA for all membranes, implying that the control of organic matrix in water before reaching NF/RO process is crucial to the performance of membrane filtration. On the other hand, all types of membrane fouling caused the decrease of PPCP rejection by NF270, especially for the hydrophilic-ionized and hydrophobic-ionized compounds at low pHs because of the shield of dominant electrostatic repulsion mechanism between PPCPs and membrane surface, causing the cake-enhanced concentration polarization phenomenon. The results were verified by dense and thick cake layers observed using scanning electron microscopy, the corresponding change of contact angles, and high adsorption amount of very hydrophobic triclosan on the active layer of NF270. However, steric hindrance and electrostatic repulsion worked synergistically for the increasing PPCP rejection by NF90 with increasing pH and membrane fouling, while steric hindrance dominates PPCP rejection by XLE. Therefore, one order less triclosan adsorption happened on membrane surface and the fouling layer of NF90 and XLE. The fouling mechanisms were illustrated using the modified Hermia model as gel layer formation for the loose NF270, intermediate blocking for NF90 and complete blocking for XLE.

Modelling of the limiting current density of an electrodialysis process by response surface methodology

Electrodialysis is an electro-membrane process for desalination, concentration, and separation in electric fields. In this process, the operating currents are limited by the concentration polarization phenomena and the limiting current density. Usually, this parameter depends on membrane and solution properties as well as on the electrodialysis stack construction. In this research paper, we will apply the Box–Behnken design in combination with response surface methodology to the development of a predictive limiting current density model. We will also study the effects of three variables related to solution composition (calcium, sulfate, and bicarbonate concentrations) on this parameter.

Concentration polarization phenomenon in the case of mechanical pressure difference on the membrane

We analyzed the transport of KCl solutions through the bacterial cellulose membrane and concentration boundary layers (CBLs) near membrane with pressure differences on the membrane. The membrane was located in horizontal-plane between two chambers with different KCL solutions. The membrane was located in horizontal-plane between two chambers with different KCL solutions. As results from the elaborated model, gradient of KCL concentration in CBLs is maximal at membrane surfaces in the case when pressure difference on the membrane equals zero. The amplitude of this maximum decreases with time of CBLs buildup. Application of mechanical pressure gradient in the direction of gradient of osmotic pressure on the membrane causes a shift of this maximum into the chamber with lower concentration. In turn, application of mechanical pressure gradient directed opposite to the gradient of osmotic pressure causes the appearance of maximum of concentration gradient in chamber with higher concentration. Besides, the increase of time of CBLs buildup entails a decrease of peak height and shift of this peak further from the membrane. Similar behavior is observed for distribution of energy dissipation in CBLs but for pressure difference on the membrane equal to zero the maximum of energy dissipation is observed in the chamber with lower concentration. We also measured time characteristics of voltage in the membrane system with greater KCl concentrations over the membrane. We can state that mechanical pressure difference on the membrane can suppress or strengthen hydrodynamic instabilities visible as pulsations of measured voltage. Additionally, time of appearance of voltage pulsations, its amplitude, and frequency depend on mechanical pressure differences on the membrane and initial quotient of KCl concentrations in chambers.

Inhibiting the concentration polarization of FO membranes based on the wettable microporous supporting layer and the enhanced dense skin layer

ABSTRACTA novel thin film composite‐type forward osmosis (FO) membrane with inhibited concentration polarization phenomenon and expectant separation performance was prepared by continuous interfacial polymerization method. The nylon‐6,6 microfiltration membrane with the average pore size of 5 μm and the self‐wetting property was for the first time used as the supporting layer of the FO membranes, which decreased the mass transfer resistance in the porous supporting layer. The skin layer was prepared via the continuous interfacial polymerization of polyamide as a relatively dense layer, with the reverse salt flux of less than 1 g/m−2 h−1. The mass transfer resistance and the reverse salt flux of the prepared FO membranes were remarkably reduced due to the functional design of the double‐layer structure, which effectively enhanced the separation selectivity and restrain the concentration polarization of the FO membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45133.

FCH2 JU projects on transport, stationary, green hydrogen

Forward osmosis (FO), is an emerging membrane technology for water desalination, wastewater treatment and diverse other applications. The technology has known growing attention mainly due to its potential for energy costs reduction. Although FO performances, expressed in terms of water flux and reverse solute flux, have been investigated for individual draw solute (DS) under a certain fixed conditions of concentration and temperature, sensitivity analysis of the impact of the DS concentration and both feed and draw solutions temperature and flowrate on the process performance have not yet been extensively addressed in the literature. In this work, a simulation approach combined with an experimental study has been conducted to evaluate the effect of operating conditions on the process performance and internal concentration polarization phenomena (ICP) using ammonium bicarbonate and sodium chloride as draw solutes. Osmotic performances of the two considered DSs were contrasted throughout the entire ranges of concentration, temperature, and cross-flow velocity. Differences between predicted and experimental results for concentration-dependent, temperature-dependent, and flowrate-dependent fluxes [Jw, Js], expressed in terms of mean absolute error have been consecutively estimated at [3.24%, 6.54%], [3.43%, 4.22%], and [6.04%, 3.08%] for NaCl, and [4.15%, 3.33%], [2.27%, 6.8%], and [5.58%, 2.87%] for NH4HCO3. Regarding ICP, the increase of concentration has shown to induce severe ICP effects causing up to 70.25% of water flux decline at 2 M NaCl. Meanwhile, increasing operating temperature have demonstrated a slight reduction of ICP; 11.63% for NaCl DS and 10.15% for ammonium bicarbonate for an increase of temperature from 10 to 35 °C.

3D printed micro/nanofluidic preconcentrator for charged sample based on ion concentration polarization

In this paper, we introduce a novel and simple method to fabricate a preconcentrator based on the ion concentration polarization phenomenon (ICP). Using a three-dimensional printed layer, the microchannels could be easily integrated with an ion exchange membrane which plays the role of the nanoporous junction needed for ICP. To demonstrate the preconcentration ability of the devices, we conducted experiments with negatively charged fluorescein sodium and positively charged rhodamine 6G. As a result, the negatively charged sample could be preconcentrated more than 18 fold by using a cation exchange membrane. The positively charged sample could be preconcentrated more than 40 fold by using an anion exchange membrane. This preconcentrator with a simple fabrication process could be implemented in various microfluidic systems for biochemical assays.

Removal of free active chlorine from synthetic wastewater by MEUF process using polyethersulfone/titania nanocomposite membrane

Abstract Micellar-enhanced ultrafiltration (MEUF) process is an alternative separation technology that employs surfactant micelles to solubilize inorganic and organic pollutants from the effluent stream. The aim of this study was to investigate the potential of this process in the removal of free active chlorine (FAC) from synthetic wastewater using polyethersulfone/titania (PES/TiO2) nanocomposite membrane. To achieve this objective, investigation was done in terms of stable permeate flux (SPF) and hypochlorite rejection efficiency (HRE) behavior of fabricated membrane, with and without hexadecyl trimethyl ammonium bromide (CTAB) as a cationic surfactant. The effects of various parameters including TiO2 nanoparticle concentration, operating time, transmembrane pressure (TMP), CTAB concentration, pH of feed solution, and feed chlorine concentration on the MEUF process performance were investigated. The results showed that ionic strength (CATB or FAC concentrations) and solution pH play different and significant role on the performance of the process. So that, SPF decreases when ionic strength of the aqueous media increases. As the pH of the solution increased, the SPF and HRE increased and decreased, respectively. The rejection efficiency increased by increasing in both TMP and nanoparticle concentration, while it was in reverse relationship with the feed chlorine concentration. According to the results, in the case of CTAB surfactant concentration, concentration polarization phenomenon is more effective than micelle formation on MEUF performance. All in all, MEUF by PES/TiO2 nanocomposite membrane has appropriate retention of FAC especially under acidic condition (pH: 2–4), as the rejection was around 75.0%. It is also clear that using TiO2 nanoparticles and cationic surfactant are useful additives in chlorine removal from wastewater and their suitable concentration are around 1.5 wt% and 0.92 mM, respectively.

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone.

The ion concentration polarization (ICP) phenomenon is one of the most prevailing methods to preconcentrate low-abundance biological samples. The ICP induces a noninvasive region for charged biomolecules (i.e., the ion depletion zone), and targets can be preconcentrated on this region boundary. Despite the high preconcentration performances with ICP, it is difficult to find the operating conditions of non-propagating ion depletion zones. To overcome this narrow operating window, we recently developed a new platform for spatiotemporally fixed preconcentration. Unlike preceding methods that only use ion depletion, this platform also uses the opposite polarity of the ICP (i.e., ion enrichment) to stop the propagation of the ion depletion zone. By confronting the enrichment zone with the depletion zone, the two zones merge together and stop. In this paper, we describe a detailed experimental protocol to build this spatiotemporally defined ICP platform and characterize the preconcentration dynamics of the new platform by comparing them with those of the conventional device. Qualitative ion concentration profiles and current-time responses successfully capture the different dynamics between the merged ICP and the stand-alone ICP. In contrast to the conventional one that can fix the preconcentration location at only ~5 V, the new platform can produce a target-condensed plug at a specific location in the broad ranges of operating conditions: voltage (0.5-100 V), ionic strength (1-100 mM), and pH (3.7-10.3).

Steady-state electrical response of homogeneous cation-exchange membrane systems under bi-ionic conditions

This paper aims to numerically study the steady-state electrical response of ion-exchange membrane systems under bi-ionic conditions. The considered particular system is constituted by a membrane with negative fixed charge and two diffusion boundary layers on both sides of the membrane. The system is bathed by two solutions with a common co-ion but different counter-ion. The ionic transport processes of a ternary electrolyte are described by the Nernst-Planck-Poisson equations not only in the membrane but also in the diffusion layers, including the electric double layers at the interfaces. The numerical results are obtained by using the network simulation method. The steady-state voltage-current characteristics are analysed for cation-exchange membrane systems with monovalent ions and systems with a divalent counter-ion. The co-ion concentration polarization phenomena in the electroneutral regions of the diffusion boundary layers of these systems are analysed and discussed in detail. The electroneutral profiles of the counter-ionic concentrations inside the membrane and the counter-ionic fluxes are also analysed for different values of the electric current through the systems.

Improving the separation performance of the forward osmosis membrane based on the etched microstructure of the supporting layer

The physical and chemical characteristics of the porous supporting layer play a key role in the separation efficiency and concentration polarization of the forward osmosis (FO) membranes. In this paper, the modified polyvinylidene fluoride (PVDF) porous membranes with high porosity and large amounts of surface membrane pores were prepared with zinc oxide (ZnO) nanoparticles as the template, and used as the supporting layer of the FO membrane. The modified FO membranes showed enhanced water permeability and separation selectivity. The increased water flux was based on the increase of the effective membrane area, and the decreased τ/ε (tortuosity factor/porosity) value obviously alleviated the concentration polarization phenomenon based on the optimization of the flow channel. The etching of the porous microstructure could reduce the limit of the supporting layer on the separation performance of the FO membrane, and provide a simple method to improve the separation efficiency of the thin film composite (TFC)-type FO membranes.

Application of a nanofibrous composite membrane to the fertilizer-driven forward osmosis process for irrigation water use

ABSTRACTIn this study, we fabricated a nanofibrous composite (NFC) membrane as a substrate to produce forward osmosis (FO) membranes, and we also assessed the use of liquid fertilizer as a draw solution for the FO process in order to produce agricultural irrigation water. Commercial cellulose triacetate (CTA) and thin-film composite (TFC) FO membranes were included in this study. Under FO tests, the NFC, CTA, and TFC membranes achieved initial osmotic water flux values of 35.31, 6.85, and 3.31 L/m2·h and final osmotic water flux values of 12.62, 6.31, and 3.85 L/m2 h, respectively. The reason for the high osmotic water flux of the NFC membrane is because its nanofiber layer has low tortuosity, high porosity, and a low thickness, resulting in a reduction in the internal concentration polarization phenomenon. When liquid fertilizer was used as the draw solution, the water flux values in the FO experiments for the NFC, CTA, and TFC membranes were 15.54, 5.46, and 2.54 L/m2 h. Finally, our results revealed that the FO process using liquid fertilizer as a draw solution can be applied to produce agricultural irrigation water from brackish water and the newly fabricated NFC membrane can be applied to the FO process.

Modeling of reverse osmosis flux of aqueous solution containing glucose

The aim of the paper is to model the permeate flux during reverse osmosis (RO) of a highly concentrated glucose solution using the osmotic pressure model. Such a model accounts for the effect of the concentration polarization phenomenon on the permeate flux. To apply this model the viscosity, the osmotic pressure of solution and the diffusion coefficient of glucose were estimated. Using mathematical simulation software, the values of mass transfer coefficient for different concentrations of glucose (5, 10, 15 and 20 wt%) and at different feed flow rate were determined. The experimental permeate flux values conducted on flat RO membranes (Type HR-99) agreed well with the values calculated by the osmotic pressure model, as shown by statistical analysis.

Measuring hydraulic layer resistance and correlated effects in colloidal fouling of salt-retaining membranes

Colloidal fouling is one of the main reasons for the reduced efficiency of membrane-based water desalination processes. The synchrony of several resistance mechanisms like hydraulic, osmotic, and electro-kinetic as well as numerous coupling effects complicate the analysis of their individual contributions to the fouling extent. A new measuring approach using a dead-end filtration test-cell allows exactly this, irrespective of any simultaneously occurring concentration polarization phenomena. First results show that the hydraulic resistance of a fully developed colloidal layer is not exclusively determined by the physicochemical properties of its constituents but seems to be strongly dependent on the specific way of its formation (e.g. ionic strength prevailing during layer build-up or filtration sequence of different particle sizes). This time-dependent effect is largely irreversible and therefore most likely due to persistent changes in fouling layer structure. A minor reversible ionic strength effect could also be demonstrated. The extent of this effect is identical irrespective of whether the ionic strength is increased or decreased. Results further indicate that commonly applied models like the Kozeny–Carman equation are lacking a size-dependent parameter that causes a disproportionate decrease of colloidal fouling layer resistance with decreasing foulant particle size.

Capillarity Based Ion Concentration Polarization for Desalination and Energy Harvesting

Ion Concentration Polarization (ICP) phenomenon is a traditional electrochemical ion transportation process near perm-selective membrane and appears as a steep concentration gradient under d.c. bias. The major function of ICP is an active ion control by an external electric field so that it is significantly useful to study the new ion transportation through nanoporous junction (or membrane) and develop novel engineering applications such as biomolecular preconcentrator and electro-desalination. Currently, the inherent capillarity of the nanostructure was demonstrated to initiate the same ICP phenomenon instead of an external power source so that a power-free desalination was achieved. This capillarity ion concentration polarization (CICP) device is shown to be capable of desalting an ambient electrolyte more than 90% without any external electrical power sources (Figure A). Theoretical analysis for both static and transient conditions are conducted to characterize this phenomenon. These results indicate that the CICP system can offer unique and economical approaches for a power-free water purification system in resource limited settings. As a reverse process of CICP, the chemical to electrical energy conversion system was successfully demonstrated as well. Since a convective flow near the perm-selective membrane plays a deterministic role for the ion transportation in both CICP and ICP mechanism, micro-pillar structures that enhance the convective flow around the membrane would accelerate the ion flux leading higher electrical current with the micro-pillar structure (Figure B). These microfluidic visualization platforms are significantly useful in both desalination and energy harvesting applications since it would provide a differential shell of such macroscopic systems that most of important ion exchanges occur microscopically. Figure A. Desalination using CICP mechanism. Figure B. current – time relation in ICP energy harvesting with and without micro pillar structures. Figure 1

Effect of poly-dispersed nanostructures on concentration polarization phenomena in ion exchange membranes

We investigated the effect of poly-dispersed nanostructures on concentration polarization (CP) phenomena in ion exchange membranes through fabrication of poly-dispersed interconnecting channels (Pd-ICs) integrated microfluidic chip and characterized the CP phenomena which happens near the interconnecting channel and main microchannel interface. Current-voltage (I-V) characteristics and depletion (enrichment) layer formation behavior within Pd-IC system are examined. We found that “Electric field focusing” affects the I-V characteristics of Pd-IC system, and Pd-IC system follows the “Limiting current occurrence” criterion. The visualization results show that the depletion layer thickness at the anodic side decreases with an increasing dispersity and also for increasing bulk concentration. We attribute this phenomena to the high electroosmotic flow in the sub-microchannel and “Electroosmosis of the second kind” at the electrolyte-membrane (Pd-IC) interface. The perm-selectivity of interconnecting channels also play an important role. At the cathodic side, we observed that fluorescent dye depleted at the microchannel and sub-microchannel interface due to the ejecting flow and current balance at the corner wedge of sub-microchannels. We hope these working mechanisms of Pd-IC system to be beneficial to model pseudo-ion exchange membrane and to develop high efficiency ion exchange membranes.

Evidence of solute-solute interactions and cake enhanced concentration polarization during removal of pharmaceuticals from urban wastewater by nanofiltration

The objective of this paper is to help understanding the distinctive influence of the matrix and of the flux decline (e.g. through the cake enhanced concentration polarization (CECP) phenomenon) on the removal mechanisms of four pharmaceutically active compounds (PhACs) from wastewater treatment plant (WWTP) effluent by nanofiltration (NF). PhACs which are commonly encountered in secondary treated effluent were spiked in various matrix (real and synthetic) to investigate the separate and synergetic effects of the organic and ionic environment on PhACs rejection by two commercial membranes (NF-90 and NF-270). With pure water, rejection of NF membranes is dependent on the type of PhACs and of the permeate flux variations. Then, it appeared that the rejection of PhACs by NF-90 was poorly influenced by the type of compounds, because of the prevalence of steric mechanisms, but rather influenced by permeate flux variations and thus to fouling. For this tight NF membrane, CECP impacts PhACs rejection at the start of filtration while after a dense cake is formed, it became enhanced. On the contrary, rejections of PhACs by the NF-270 were enhanced during the filtration of the real wastewater in comparison with spiked pure water. It appeared that for loose-NF membranes, PhACs rejection is mainly governed by solute-solute interactions (EfOM-compound association) or electrostatic membrane-solute interactions. Finally, it seems that calcium concentration of the effluent is a critical parameter for the rejection of PhACs as it alters both the availability of sites for PhACs association and the fouling layer density. Rejections of the NF-270 were negatively impacted in the presence of Ca2+. Such a study has practical implications for further understanding of the fate of trace organic compounds during nanofiltration of wastewater for reuse applications.